1. Field of the Invention
This invention relates to a method for in situ repairing of leaks in in-service conduits or containers. In one aspect, this invention relates to a method for in-situ repairing of leaks in in-service utility pipelines. In one aspect, this invention relates to a method for in-situ repairing of leaks in in-service natural gas pipelines.
2. Description of Related Art
Mechanical couplings and fittings, e.g., tees, valves, elbows, etc. are used widely throughout the natural gas industry in association with steel, cast iron, and plastic pipelines. Mechanical couplings and fittings generally all share a similar design in that rubber seals are compressed around pipes to be plumbed to create a seal. One disadvantage of this design is the lack of substantial axial (pullout) restraint for many of the coupling and fitting designs (types). After years of service, these couplings or fittings may develop a leak due to thermal expansionlcontraction of the pipeline, relaxation of the rubber seals, corrosion, or even gas composition changes. Indeed, recent failures of mechanical couplings have heightened concerns about their continued safety in natural gas distribution systems. Thus, it is desirable to have a means for remediating leaking mechanical couplings and fittings without having to remove the coupling or shut down the pipeline. It is also highly desirable to have the option of adding axial restraint at the same time. It will be appreciated that the ability to perform a repair without removing the coupling or fitting, without shutting down the pipeline, and without using bypass or cut-out methods for maintaining fluid flow would both save time and reduce costs associated with shutting down the pipeline.
Numerous methods for sealing connecting pipe sections and leaks are taught in the prior art. See U.S. Pat. No. 6,276,726 which teaches a pipe clamp closing over a leak; U.S. Pat. No. 5,372,391 which teaches an internal pipe attachment mechanism which employs a sealing assembly that is set by crushing the sealing assembly through setting of the mechanical connection between pipe sections; U.S. Pat. No. 4,713,870 which teaches insertion of an expandable sleeve into a pipe and expanding the sleeve against the pipe wall containing the leak to cover and, thus, seal the leak; and U.S. Pat. No. 4,652,023 which teaches a repair coupling employing a sealing liner having circumferential ribs which seal against the pipe wall on both sides of the leak to effectively isolate the leak. While all of these sealing methods address the problem of repairing a leak in a pipe, none of the methods results in a permanent plugging of the leak.